Dehydrator



June 15, 1943. ROBERTS DEHYDRATOR Filed Nov. 14, 1941 2- Sheets-Sheet 2 Q m F Q mfi v Q m w .M N N r In 5 m. MN m m. x 1% 3 3 $31 E E 3/ j 3/ E j i J I fi l k v Q Q Q N. x Q v N m Q a w E E v Q NN T Patented June 15, 1943 UNITED STATES ATENT OFFICE DEHYDRATOR Earle L. Roberts, Modesto, Calif.

Application November 14, 1941, Serial No. 419,137

Claims.

This invention relates to dehydrators of the tunnel type, through which trucks, carrying stacks of drying trays of the produce to be dehydrated, are moved in step by step order.

One of the major objects of this invention is to provide a dehydrator in which the drying air flows in such a manner over the trays as to provide a very even and thorough drying action, so that there is no oxidizing action on the produce, and a greater percentage of the natural sugar is retained; the necessity of lye-dipping and similar treatment of the produce is eliminated, while the dry produce appears to be worm-proof.

Also, the air flow is controlled in such a manner that there is a better conservation of air than heretofore obtained, and as a result a lesser expense for heat and power for circulating the air is required.

In connection with the air circulating arrangement, another object is to provide an air circulating fan unit so arranged as to draw simultaneously from one end and both sides of the tunnel, to mix said air with freshly heated air, and to then discharge the air in equal quantities into both sides of the tunnel toward the opposite end. Also, the fan unit itself is arranged so that end thrust is eliminated, and it takes less power to operate it than the usual fan.

A further object of the invention is to produce a simple and inexpensive device and yet one which will be exceedingly effective for the purpose for which it is designed.

These objects I accomplish by means of such structure and relative arrangement of parts as will fully appear by a perusal of the following specification and claims.

In the drawings similar characters of reference indicate corresponding parts in the several views:

Figure 1 is a sectional plan of my improved dehydrator.

Figure 2 is a longitudinal section on the line 2-2 of Fig. 1.

Figure 3 is a similar view on the line 3-3 of Fig. 1.

Referring now more particularly to the characters of reference on the drawings, the dehydrator comprises a relatively long rectangular dehydrator tunnel I included between parallel side walls 2 which are spaced apart a greater distance than the width of the trucks 3 and stacks of trays 4 thereon which are to be passed through the tunnel. The trucks are of the usual wheeled variety, and run on rails 5 extending lengthwise through the tunnel centrally thereof. As usual, the trays when stacked are closed on their sides,

but provide open passages at their ends, as shown in Fig. 1, so that the air can circulate between the trays lengthwise of the trucks and tunnel. Also, the trays are slightly shorter than the trucks, so that when the latter are disposed in abutting end to end relation, there is a space between the various stacks of trays.

At the truck discharge end, the tunnel is closed by doors 6, but at its intake end permanent end walls 1 only extend from the side walls to adjacent the line of the side edges of the trays, the remainder of said end being open from top to bottom except for a removable closure board 8 extending from the floor to the level of the top of the trucks, and placed in position against the endmost truck after the latter is in the tunnel.

Disposed. under and covered by the floor 9 of the tunnel substantially centrally of its length is a fan chamber I0, which extends from side to side of the tunnel. Troughs l I, one on each side of the tunnel, lead downwardly from rail level adjacent the intake end to the adjacent end of the fan chamber at the level of the bottom the-reof. Communication between said troughs and the fan chamber is had by means of adjustable ports [2 in the side walls of the troughs leading into a mixing chamber l3 ahead of the chamber I9, and communicating therewith by a central port 14 in the wall l5 therebetween.

A furnace [6 of suitable character is disposed outside the tunnel on one side thereof, and has a heat conducting passage ll leading into the mixing chamber l3. Other troughs l8 slope upwardly between th side walls of the tunnel and the track from the opposite end of the fan cham ber to rail or floor level adjacent the discharge end of the tunnel, said troughs l8 being freely open tothe fan chamber from top to bottom thereof. A fresh air intake conduit l9, having an adjustable entry gate outside the tunnel, extends under one trough l8 and discharges into a chamber 20 disposed beyond the corresponding end of the fan chamber and communicates therewith by means of a centrally disposed port 2| in the wall 22 therebetween, the ports M and 2| being pref erably alined.

Mounted in the fan chamber is a fan unit by means of which air is circulated through the tunnel. This unit comprises a pair of fans 23 spaced apart in the chamber transversely of the tunnel and mounted on a transversely extending shaft 24. This shaft projects into an enclosure 25 externally of the tunnel on one side thereof, and which contains'the operating motor 26 or similar driving means for said shaft.

The fans are of the type adapted to throw air in a direction substantially parallel to their axis, and are set with their blades in oppositely pitched relation as shown, and in such a direction relative to the direction of rotation of the drive shaft that air will be drawn into the fans between the same and then forced into opposite directions from the fans. The ports l4 and 2i, which are the air intake ports for the same chamber, are disposed centrally between the fans.

In operation, the trucks are moved into the tunnel through the intake end, sufficient trucks being initially inserted to extend substantially one-half of the length of the tunnel, or so that the innermost truck adjacent its inner end projects beyond vertical baffle walls 21 in the tunnel. Said walls are disposed between the adjacent end of troughs H and I8 and. extend from the floor to the roof of the tunnel, and as close to the trucks and trays thereon as possible. When the trucks are thus in place, the tunnel is practically divided into two separated front and rear sections or chambers, as will be evident.

After the trucks are inserted, the removable board or baflie 8 is placed in position to form a closure between the floor and the end of the adjacent truck as shown in Fig. 2. It will be understood that the rearmost truck in the row-is disposed so that its rear end is substantially in line with the walls I. The side passages in the tunnel above the troughs H are therefore closed by the trays, but at th same time the spaces between the trays of the rearmost truck are open at their rear end to atmosphere outside the tunnel. As the drying proceeds, another truck is inserted, advancing those already in the tunnel a corresponding distance, until the latter is filled. Thereafter, as each fresh truck is inserted, one is removed from the discharge end of the tunnel, with the produce thereon in a sufficiently dehydrated condition.

With the operation of the fan unit, fresh, cool air is drawn only as may be required into the fans from the outside through the conduit I9 and port 2!. A certain amount of air which has already circulated through the trays and which is now reheated by the hot blast or products of combustion from the furnace at the point where such blast discharges into the chamber I3, is also drawn into the fans from the front section of the tunnel through the troughs H, ports l2, chamber l3 and port M, as indicated by the arrows A. Such air passes into the open-topped troughs from the space between the trays of adjacent trucks by reason of the fan suction.

Due to the opposed relationship of the fans, the hot and cold air as drawn in from opposite sides thereof becomes thoroughly mixed, and is then discharged in opposite directions from the fans in the form of two streams, which enter and are forced along the troughs I8. 'Ilbese air streams are prevented from being directly forced into the front section of the tunnel by reason of troughs H as previously described; the amount of air thus returned being governed by the extent of opening of the ports l2. At the same time a certain amount of the air being forced to the intake end of the tunnel from between the trays may escape into the atmosphere, depending on th pressure differential between outside atmosphere and the air inside the tunnel.

By reason of the above described air circulating arrangement, a great conservation of air and heat are obtained; and due to the construction of the fan unit and its relation to the various air ports, air streams of evenly heated temperature are distributed in even quantities into the troughs It at both sides of the line of trays, so that the dehydrating action thereon is very even and effective.

It will also be seen that the fresh tray loads which are inserted last are not subjected to the freshly heated air, which would tend to dry the produce too rapidly. Instead, such loads are gradually dried with increasing intensity only as they are moved further into Uhe tunnel, until just as the dehydrating action is completed, the tray load next to be withdrawn from the tunnel is subjected to the full volume of freshly heated and dry air. I have found this to be extremely effective in attaining a dehydrated product of first class quality, in which no oxidizing of the natural sugar is had, and a much greater percentage of the sugar is retained than is ordinarily the case. Also, the end thrust of the two fans counteracting each other cause less friction to be developed, and consequently less power is necessary to operate the same.

From the foregoing description it will be readily seen that I have produced such a device as substantially fulfills the objects of the invention as set forth herein.

While this specification sets forth in detail the present and preferred construction of the device, still in practice such deviations from such detail may be resorted to as do not form a departure from the spirit of the invention, as defined by the appended claims.

Having thus described my invention, what I claim as new and useful and desire to secure by Letters Patent is:

1. A dehydrator of the tunnel type adapted to receive a row of open-ended stacked drying trays therein, said trays being intermittently movable through the tunnel from the intake toward the discharge end thereof; the tunnel including a floor, side walls spaced apart a greater distance than the width of the trays, a closure for the tray discharge end of the tunnel and end walls at the intake end extending laterally inward from the side walls to adjacent the planes of the side edges of the stacks of trays whereby to leav an, outlet from the tunnel from between the trays of the adjacent endmost stack; longitudinal open-ended troughs depressed in the floor of the tunnel adjacent the side walls and extending downwardly from floor level adjacent the discharge end of the tunnel to a termination intermediate the ends of the tunnel, similarly disposed troughs extending downwardly from floor level adjacent the intake end of the tunnel to a termination short of the adjacent end of the first named troughs, air heating means, and air circulating means having discharge openings communicating with the first named troughs at said termination thereof and having intake openings communicating with the last named troughs adjacent said termination thereof whereby air will be circulated through the trays in series from the tray discharge end of the tunnel toward the intake end thereof.

2. A dehydrator of the tunnel type adapted to receive a row of open-ended stacked drying trays therein, said trays being movable intermittently through the tunnel from the intake toward the discharge end thereof; the tunnel including a floor, side walls spaced apart a great er distance then the width of the trays, a closure for the tray discharge end of the tunnel and end walls at the intake end extending laterally inward from the side walls to adjacent the planes of the side edges of the stacks of trays whereby to leave an outlet from the tunnel from between the trays of the adjacent endmost stack; a 1ongitudinal open-ended trough depressed in the floor of the tunnel adjacent one side wall and extending from adjacent the discharge end of the tunnel to a termination intermediate the ends of the tunnel, a similarly disposed trough extending from adjacent the intake end of the tunnel to a termination short of the adjacent end of the other trough, air heating means and air circulating means communicating with the troughs adjacent their terminations and arranged to cause the air to be forced along the first named trough toward the discharge end of the tunnel, circulated through the trays in series from the discharge end of the tunnel to the intake end thereof, and mainly returned to the circulating means along the last named trough.

3. A dehydrator as in claim 2, including vertical baflie walls extending laterally inward from the side walls intermediate the adjacent terminations of the troughs to adjacent the sides of the row of trays.

4. A dehydrator of the tunnel type adapted tc receive a row of open-ended stacked drying trays therein in end to end spaced relation, the tunnel including side walls spaced apart a greater distance than the width of the trays, a closure for the discharge end of the tunnel, end walls at the intake end of the tunnel extending laterally inward from the side walls to adjacent the planes of the side edges of the stacks of trays, and bafile walls extending laterally inward from the side walls intermediate the ends of the tunnel and disposed so as to be intermediate the ends of one stack of trays, a fan chamber disposed below the tunnel adjacent the bafile walls. said chamber having an intake opening and a pair of transversely spaced discharge openings, an air circulating fan in said chamber, means to heat the air as it is circulated, passage means leading to said intake opening from the portion of the tunnel between the baffle walls and the intake end of the tunnel and arranged to cause air to travel to the chamber from the intake end of the tunnel along the sides of said tunnel, and open-topped troughs leading lengthwise of the tunnel at the side thereof below the floor level of the tunnel with an upward slope on the bottom toward the discharge end of the tunnel and communicating at their lower end with the discharge openings of the fan chamber whereby the air from the fan chamber will travel first toward the discharge end of the tunnel, will be then circulated in series through the trays in the direction of the intake end of the tunnel, and will then be returned to the fan chamber.

5. A dehydrator of the tunnel type adapted to receive a row of open-ended stacked drying trays therein in end to end spaced relation, the tunnel including side walls spaced apart a greater distance than the width of the trays, a closure for the tray discharge end of the tunnel, end walls at the intake end of the tunnel extending laterally inward from the side walls to adjacent the planes of the side edges of the stacks of trays, and baflie walls extending laterally inward from the side walls intermediate the ends of the tunnel and disposed so as to be intermediate the ends of one stack of trays, a fan chamber disposed below the tunnel adjacent the baflie walls, said chamber having an intake opening and a pair of transversely spaced discharge openings, an air circulating fan in said chamber, a mixing chamber with which said intake opening communicates, means to supply heat to said mixing chamber, passage means extending along the portion of the tunnel between the baffle walls and the intake end of the tunnel at the sides of the latter, the mixing chamber having transversely spaced intake openings communicating directly with said passage means, and means forming separate passages leading along the sides of the tunnel between the heme walls and the discharge end ofthe tunnel from and di-- rectly communicating at one end with the discharge openings oi the fan chamber.

EARLE L. ROBERTS. 

